The UBAP1 Subunit of ESCRT-I Interacts with Ubiquitin via a SOUBA Domain

Abstract

SummaryThe endosomal sorting complexes required for transport (ESCRTs) facilitate endosomal sorting of ubiquitinated cargo, MVB biogenesis, late stages of cytokinesis, and retroviral budding. Here we show that ubiquitin associated protein 1 (UBAP1), a subunit of human ESCRT-I, coassembles in a stable 1:1:1:1 complex with Vps23/TSG101, VPS28, and VPS37. The X-ray crystal structure of the C-terminal region of UBAP1 reveals a domain that we describe as a solenoid of overlapping UBAs (SOUBA). NMR analysis shows that each of the three rigidly arranged overlapping UBAs making up the SOUBA interact with ubiquitin. We demonstrate that UBAP1-containing ESCRT-I is essential for degradation of antiviral cell-surface proteins, such as tetherin (BST-2/CD317), by viral countermeasures, namely, the HIV-1 accessory protein Vpu and the Kaposi sarcoma-associated herpesvirus (KSHV) ubiquitin ligase K5.

VPS37 Isoforms Differentially Modulate the Ternary Complex Formation of ALIX, ALG-2, and ESCRT-I

“…29,30) One report, however, suggests that UBAP1 favors VPS37A when assembling ESCRT-I complexes and functions in the sorting of EGFR to MVB, but not in cytokinesis. 30) This accords with the selective interaction of UBAP1 with HD-PTP, a paralog of ALIX involved in MVB sorting.…”

A Pseudomonas aeruginosa TIR effector mediates immune evasion by targeting UBAP1 and TLR adaptors

“…TNFR1 inhibition was specific to PumA as expression of the Brucella TIR domain‐containing protein BtpA/TcpB did not have any significant effect (Fig EV5B). We therefore carried a yeast two‐hybrid screen to identify an alternative target of PumA and found UBAP1, a key component of the ESCRT‐I mediating trafficking and sorting of ubiquitinated cargo proteins on MVBs (Stefani et al , 2011; Agromayor et al , 2012). This interaction was confirmed by co‐IP from cells co‐expressing PumA and UBAP1 (Fig 6A and B) as well as by pull‐down using purified PumA or PumA 1–136 and cell extracts with either streptavidin‐tagged UBAP1 (Fig 6C) or Myc‐UBAP1 (Appendix Fig S5A).…”

“…All yeast two‐hybrid preys identified in our screen encoded for a region containing amino acid 45–164, present between two key functional domains: the N‐terminal UBAP1‐MVB12‐associated (UMA) domain (residues 17–63) that binds the central stalk of ESCRT‐I Vps37 and the central domain (residues 159–308), containing the recently identified key binding site for HDPTP which can act as a cargo adaptor (Gahloth et al , 2016). The C‐terminal portion of UBAP1 includes a SOUBA domain (residues 381–502) known to bind ubiquitin (Agromayor et al , 2012). UBAP1 is a key component of ESCRT‐I that enables sorting of ubiquitinated cargo on MVBs.…”

“…UBAP1 is known to play a key role in selective sorting of ubiquitinated endosomal cargo on multi‐vesicular bodies (MVB), via its interaction with VPS37A and other components of ESCRT‐I namely TSG101 (Wunderley et al , 2014), as well as with the ESCRT regulator, His domain protein tyrosine phosphatase (HDPTP; Stefani et al , 2011). UBAP1 has been shown to control endosomal sorting of ubiquitinated EGFR (Stefani et al , 2011) as well as ubiquitin‐dependent degradation of antiviral surface proteins (Agromayor et al , 2012) and integrins (Kharitidi et al , 2015). More recently, UBAP1 was shown to modulate steady‐state trafficking of cytokine receptors in non‐stimulated cells (Mamińska et al , 2016).…”

“…More recently, UBAP1 was shown to modulate steady‐state trafficking of cytokine receptors in non‐stimulated cells (Mamińska et al , 2016). UBAP1 is expressed in a wide range of tissues, but when deleted in mice, it is lethal for embryos (Agromayor et al , 2012). …”